Natural History of Community-Acquired Methicillin-Resistant Staphylococcus aureus Colonization and Infection in Soldiers

• Published in: Clinical infectious diseases Vol. 39; no. 7; pp. 971 - 979
• Main Authors: Ellis, Michael W., Hospenthal, Duane R., Dooley, David P., Gray, Paula J., Murray, Clinton K.
• Format: Journal Article
• Language: English
• Published: Chicago, IL The University of Chicago Press 01.10.2004; University of Chicago Press
• Subjects: Abscess - microbiology; Abscesses; Adolescent; Adult; Anti-Bacterial Agents - pharmacology; Antibacterial agents; Antibiotics; Antibiotics. Antiinfectious agents. Antiparasitic agents; Bacterial diseases; Biological and medical sciences; Carrier State; Cellulitis - microbiology; Community-Acquired Infections - drug therapy; Community-Acquired Infections - epidemiology; Female; Forts; Hospital admissions; Human bacterial diseases; Humans; Infections; Infectious diseases; Major Articles; Male; Medical sciences; Methicillin Resistance; Methicillin resistant staphylococcus aureus; Microbial colonization; Military Personnel; Nose - microbiology; Pharmacology. Drug treatments; Predisposing factors; Prospective Studies; Risk Factors; Soldiers; Staphylococcal Infections - drug therapy; Staphylococcal Infections - epidemiology; Staphylococcal infections, streptococcal infections, pneumococcal infections; Staphylococcus aureus; Staphylococcus aureus - drug effects; Staphylococcus aureus - genetics; Staphylococcus aureus - pathogenicity; Virulence Factors - genetics; Army; Prevalence; Drug susceptibility test; Samplings; Method; Eradication; Epidemiology; Case history; In vitro; Infection; Community acquired infection; Gene; Medical prescription; Risk factor; Bacteriosis; Bacteria; Micrococcales; Micrococcaceae; Soft tissue; Antibacterial agent; Sampling; Staphylococcal infection; Colonization; Staphylococcus aureus
• ISSN: 1058-4838; 1537-6591; 1537-6591
• DOI: 10.1086/423965

Background. Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is an emerging pathogen for which the prevalence, risk factors, and natural history are incompletely understood. Methods. In this prospective observational study, we evaluated 812 US Army soldiers to determine the prevalence of and risk factors for CA-MRSA colonization and the changes in colonization rate over time, as well as to determine the clinical significance of CA-MRSA colonization. Demographic data and swab samples from the nares for S. aureus cultures were obtained from participants at the start of their training and 8–10 weeks later. Over this time period, participants were observed prospectively to monitor for soft-tissue infections. S. aureus isolates were characterized by in vitro examination of antibiotic susceptibilities, mecA confirmation, pulsed-field gel electrophoresis, and Panton-Valentine leukocidin (PVL) gene testing. Results. At the initial sampling, 24 of the participants (3%) were colonized with CA-MRSA, 9 of whom (38%) developed soft-tissue infections during the study period. In contrast, 229 participants (28%) were colonized with methicillin-susceptible S. aureus (MSSA), 8 (3%) of whom developed clinical infections during the same period (relative risk, 10.7; 95% confidence interval, 4.6–25.2; P < .001). At follow-up culture, the CA-MRSA colonization rate dropped to 1.6% without eradication efforts. Previous antibiotic use was a risk factor for CA-MRSA colonization at the initial sampling (P = .03). PVL genes were detected in 66% of 45 recovered CA-MRSA isolates, including all 9 clinical isolates available for analysis. Of subjects hospitalized, 5 of 6 had PVL-positive CA-MRSA infections. Conclusions. CA-MRSA colonization with PVL-positive strains was associated with a significant risk of soft-tissue infection, suggesting that CA-MRSA may be more virulent than MSSA. Previous antibiotic use may play a role in CA-MRSA colonization.